Addition of Grignard reagents to formaldehyde to give primary alcohols
Description: Addition of a Grignard reagent to formaldehyde results in a new C–C bond and a primary alcohol (after addition of acid)
Notes: X here can be Cl, Br, or I. The purpose of acid is to protonate the negatively charged oxygen after addition. Its precise identity can vary.
Notes: Note that the acid here can be strong acids such as H3O(+), H+, or H2SO4
Mechanism: 1,2-addition of the Grignard to the carbonyl (Step 1, arrows A and B) results in a negatively charged oxygen (“alkoxide”) which is protonated when acid is added in the workup (Step 2, arrows C and D) resulting in the primary alcohol.
Notes: There’s nothing special about the chloride or bromide ions here; any halogen (except fluoride) will do.